Deuterium relaxation

Void R R and Void R L 1991 Deuterium relaxation in moieouiar solids Adv. Magn. Opt. Reson. 16 85-171... 

The rotational correlation time can be directly obtained from 13C or deuterium relaxation measurements on a diamagnetic analogue (Y(III), La(III) or Lu(III)) of the Gd(III) complex [38,70-72]. One disadvantage is low sensitivity of 13C or 2D at natural abundance. Moreover, these methods do not measure the rotation of the metal - coordinated water vector, important from the practical point of view, and this may cause problems mainly in the case of large molecules. 

Self diffusion coefficients of deuterated toluene were measured, rather than protonated toluene in order to minimize the experimental difficulties associated with very long proton spin lattice relaxation times (T- ). Since the value of the T1 determines the length of time between pulse sequences, a long relaxation time leads to prohibitively long measurement times. Previous measurements (36-38) of proton and deuterium relaxation times in liquid toluene have been made as a function of temperature and pressure. The relaxation is due to dipolar interactions in protonated toluene and quadrupolar interactions in toluene-dg. Therefore, the relaxation times can be expected to increase with increasing temperature. However, the quadrupolar relaxed deuterium T. values are smaller than the proton T1... 

Another source of microdynamic information comes from the deuterium relaxation rates. The quadrupolar coupling constant (e2qQ/h) expresses the magnitude of the coupling between the electric quadrupole moment Q of the nucleus and the efg q at the nucleus (e is the electronic charge, and h is Planck s constant). It provides a relaxation mechanism for the quadrupolar nucleus of its Fourier component at the Larmor (resonance) frequency for this nucleus is non-negligible. It has such a Fourier component because tumbling of the molecule the quadrupolar nucleus is part of, in a... 

Deuterium nmr describes in equally clear-cut and elegant a manner the static (order parameter) and the microdynamic (correlation time t ) properties of hydrocarbon chains in aggregated surfactants 13). The example of octanoate, in various phases, resembles the membrane behavior of phospholipids a decrease of the order parameter is found for deuterium relaxation rates,... 

For selectively deuterated compounds, an interesting opportunity is offered by polarization transfer from 2H as demonstrated for 13C INEPT and DEPT142 among the advantages of the method is that all probes have the needed deuterium lock coil. Of course, the last-mentioned experiment can enhance the silicon signal only due to rapid deuterium relaxation but can be useful for line assignment through selective deuteration. 

VanderHart DL. Study of molecular reorientation pressure and temperature dependence of deuterium relaxation in liquid CDCI3. J Chem Phys 1974 60 1858-1870. 

Answer The p-pinene molecule is small, roughly spherical and lacking in polar functional groups. It can therefore tumble very rapidly in solution without perturbing surrounding solvent molecules. This rapid tumbling leads both to inefficient proton relaxation by the dipole-dipole mechanism, so that NOEs are too small to measure easily ( 6.2.1 and 6.4.3), and to relatively slow deuterium relaxation, which gives sharp deuterium lines ( 7.2.3). 

This has been reported (308) to be small because the deuterium relaxation is dominated by its quadrupole moment. 

Top) Solid-state proton (left) and deuterium (right) NMR spectra for freeze-dried media systems containing 14% mannitol indicating narrow (rapidly exchanging) and broad (slowly exchanging) components. (Bottom) Tj and T2 deuterium relaxation times for freeze-dried xanthan-locust bean gum with (solid circles) and without (solid squares) 14% mannitol. 

Hills, B.P. Multinuclear NMR studies of water in solutions of simple carbohydrates I. Proton and deuterium relaxation. Mol. Phys., 72, 1099, 1991. 

As in the case of H, the T, time of deuterium can be obtained with the inversion - recovery (180° - x - 90°) experiments. The standard treatment of the collected data [16] as monoexponential NMR decays provides a quite good accuracy in the T, determination with errors < 5% [16]. Note that a non -exponential or biexponential deuterium relaxation in solution is rather a rare phenomenon [18]. 

As quadrupole relaxation dominates deuterium relaxation hlgh-resolutlon NMR In liquids will be confined to small and medivun-sized molecules where relaxation broadening Is moderate. Assuming for example a correlation time of 10 sec as it is typical of a molecule of MH 250, a natural line width of 1.5 Hz results based upon a quadrupole coupling constant of 180 kHz. 

Both direct and Indirect methods have been used to measure deuterium relaxation (2) the Inversion-recovery or partially relaxed Fourier transform method Is most widely employed. 

The rotational correlation times of guest compounds in CD complexes are usually-prolonged. Thus, both C and deuterium relaxation times provide significant information on the dynamics of ligand-CD complexes and may also be used for the determination of the association constant [59], [60], [61]. This is especially useful in those cases when the data about the dynamics are not accessible from line-shape analysis. Recently available resonance ROESY techniques also allow a semiquantitative estimation of internal motions in ligand-CD complexes [2]. 

Greenfield. M.S. Void. R.L. Void. R.K. Deuterium relaxation and vibrationally averaged quadrapole coupling in an alkane/urea clathratc. J. Chem. Phys. 1985. 83. 1440. 

Figure 23 Temperature dependence of the deuterium relaxation rate difference. A/ , measured with deuterium-labeled C12E5, in the ternary C12E5-water-decane system. The two volume fractions, (1) = 0.23 and 0.12, respectively, refer to the total volume fraction of surfactant and oil for a constant surfactant/oil ratio 0 /0 = 0.815. At lower temperatures the system forms spherical oil droplets in water and AR is the same for the two volume fractions. Above a certain temperature, the droplets grow in size as demonstrated by the increase in AR. (Data from Ref. 58.)...

To study the solvent behavior in the presence of a bonded moiety, it is necessary to use deuterated solvents since deuterium is a quadrupolar nucleus whose relaxation is controlled by the molecular correlation time, a measure of molecular motion [37]. The C-18 bonded phase has been studied in water/methanol and water/acetonitrile mixtures of varying composition [38]. Figure 10 illustrates one part of this study where the change in the deuterium relaxation time in D2O is monitored as a function of % organic modifier in the mobile phase for methanol and acetonitrile using two different bonding density C-18 stationary phases. These results show that little change in the deuterium... 

E. Lang, H.-D. Luedemann, Rressure and temperature dependence of the longitudinal deuterium relaxation times in supercooled heavy water to 300 MRa and 188 K, Ber. Bunsenges. Rhys. Chem. 84(1980)462-470. 

Deuterium relaxation times have been used to study molecular complexation and binding interactions (1,2). The transverse relaxation time, T2, has recently been used to study substrates and inhibitors interacting with soybean lipoxygenase (10). The expression for T2 is given by eq. 5, in which o)q is the H Larmor... 

Overall molecular reorientations and internal motions take place in the 10 10 s time window and information about them can be accessed using relaxation rate measurements. By far the best approach is to use NMR experiments where deuterium Zeeman and quadrupolar spin-lattice relaxation times are measured on selectively deuteriated mesogens or on deuteriated probes dissolved in the mesophase. Frequency, orientation and temperature dependence of the spectral densities obtained in these relaxation studies give indications about the various motional modes and are extremely useful for testing orientational diffusion and chain dynamics models. Different deuterium relaxation experiments can be employed to extend the observable dynamic range the quadrupolar echo sequence gives spin-spin relaxation times sensitive to motions in the range s, while extremely slow motions... 

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